When rosamicin is subjected to mild acylating conditions, it forms monoesters at position 2'. Under more rigorous acylating conditions 3,2'-diesters are formed. Attempted hydrolyses of such diesters to produce 3-monoesters, under the hydrolytic conditions normally used in the art, cause one or more of several reactions to take place, e.g. both acyl functions are removed yielding the unacylated antibiotic, the lactone moiety of the aglycone hydrolyzes to yield an open-chain compound, the glycoside moiety is removed and gross degradation of the aglycone occurs. Generally, two or more of the foregoing reactions take place concurrently thereby giving rise to a plethora of undesired by-products. None of the prior art hydrolytic conditions provide a suitable method for obtaining the desired 3-monoesters. I have discovered a procedure which provides a facile means for preparing the previously unobtainable 3-monoesters of rosamicin.